A one-dimensional equivalent linear method （EQL） is widely used in estimating seismic ground response. For this method, the shear modulus and damping ratio of inelastic soil are supposed to be frequency independent....A one-dimensional equivalent linear method （EQL） is widely used in estimating seismic ground response. For this method, the shear modulus and damping ratio of inelastic soil are supposed to be frequency independent. However, historical earthquake records and laboratory test results indicate that nonlinear soil behavior is frequency- dependent. Several frequency-dependent equivalent linear methods （FDEQL） related to the Fourier amplitude of shear strain time history have been developed to take into account the frequency-dependent soil behavior. Furthermore, the shear strain threshold plays an important role in soil behavior. For shear strains below the elastic shear strain threshold, soil behaves essentially as a linear elastic mate- rial. To consider the effect of elastic-shear-strain-threshold- and frequency-dependent soil behavior on wave propaga- tion, the shear-strain-threshold- and frequency-dependent equivalent linear method （TFDEQL） is proposed. A series of analyses is implemented for EQL, FDEQL, and TFDEQL methods. Results show that elastic-shear-strain-threshold- and frequency-dependent soil behavior plays a great influence on the computed site response, especially for the high- frequency band. Also, the effect of elastic-strain-threshold- and frequency-dependent soil behavior on the site response is analyzed from relatively weak to strong input motion, and results show that the effect is more pronounced as input motion goes from weak to strong.展开更多
To provide reference for selenium resource exploitation of soil,many selenium-tolerant strains were isolated from selenium-rich soil in Guangxi. The dilution spread plate method and selenium-added culture method were ...To provide reference for selenium resource exploitation of soil,many selenium-tolerant strains were isolated from selenium-rich soil in Guangxi. The dilution spread plate method and selenium-added culture method were used to screen the selenium-tolerant strains from the soils which were sampled from the main Selenium-rich areas such as Yongfu,Bama,Yulin Hanshan,Guiping and Tengxian. The results showed that 8 strains with high selenium tolerance were obtained,which could tolerate the selenium concentration above 10 000 μg/m L in solid medium. Among the 8 strains,YLB1-33 showed the highest selenium tolerance,and it could still grow weakly in the solid medium with selenium concentration of 29 000 μg/m L. The sequencing of 16 S rD NA and phylogenetic analysis showed that YLB1-6 was identified as Bacillus cereus,BMB2-1 and TXB1-8 were identified as Bacillus pumilus,GPB2-5 was identified as Bacillus thuringiensis,YLB1-26 and YLB1-33 were identified as Bacillus licheniformis,and YLB1-2 and YFB1-8 were identified as Serratia marcescens. The finding of selenium-tolerance strains had potential application value on promoting the utilization of selenium soil resources and the development of selenium-rich agricultural products in Guangxi.展开更多
This paper presents an alternative analytical technique to study a plane strain consolidation of a poroelastic soil by taking into account the anisotropy of permeability. From the governing equations of a saturated po...This paper presents an alternative analytical technique to study a plane strain consolidation of a poroelastic soil by taking into account the anisotropy of permeability. From the governing equations of a saturated poroelastic soil, the relationship of basic variables for a point of a soil layer is established between the ground surface （z=0） and the depth z in the Laplace-Fourier transform domain. Combined with the boundary conditions, an exact solution is derived for plane strain Biot＇s consolidation of a finite soil layer with anisotropic permeability in the transform domain. Numerical inversions of the Laplace transform and the Fourier transform are adopted to obtain the actual solution in the physical domain. Numerical results of plane strain Biot＇s consolidation for a single soil layer show that the anisotropic of permeability has a great influence on the consolidation behavior of the soils.展开更多
A new semi-empirical formula for evaluating the residual strain of soils under earthquake loading is presented in this paper based on the incremental method and the increment model proposed by the authors.When the inc...A new semi-empirical formula for evaluating the residual strain of soils under earthquake loading is presented in this paper based on the incremental method and the increment model proposed by the authors.When the incident loading is uniform,the results calculated by the new formula are nearly the same as those by the existing formula.For excitation of the random earthquake loading,the results calculated by the new formula are compared to the results obtained by dynamic triaxial tests.The dynamic triaxial tests had been performed considering different seismic waves,confining stresses, consolidation ratios,and types of cohesive soils.The comparison between the calculated and tested results indicate that the presented formula can efficiently and practically describe the time-dependent process of the soil residual strains under actual seismic loads.展开更多
[Objective] The aim was to screen strains producing alkaline protease from soil and study the conditions for enzyme production.[Method] Eight strains producing alkaline protease were isolated from soil through plate i...[Objective] The aim was to screen strains producing alkaline protease from soil and study the conditions for enzyme production.[Method] Eight strains producing alkaline protease were isolated from soil through plate isolation,and the ability of enzyme production was measured by filter paper and Folin-phenol method.The strain with the strongest ability of enzyme production was screened as a candidate strain,then the factors influencing the ability of enzyme production was studied,finally the conditions for enzyme production was optimized through orthogonal test.[Result] No.5 strain was screened as a candidate strain due to its strong ability of enzyme production(6.00 U/ml),which accounted for 134.1% of that of Bacillus licheniformis,and it was gram-positive bacterium belonging to Clostridium.Orthogonal test showed that the optimal condition for producing protease was an environment with pH=11,0.3% of sucrose and 0.8% of peptone in the fermentation medium,and inoculation amount was 105 cfu/ml.In addition,peptone had significant impact on the level of enzyme production.[Conclusion] The study could provide theoretical references for the screening of strains producing alkaline protease.展开更多
In the light of matrix theory, the character of stress increment which causes the rotation of principal stress axes is analysed and the general stress increment is decomposed into two parts: coaxial part and rotationa...In the light of matrix theory, the character of stress increment which causes the rotation of principal stress axes is analysed and the general stress increment is decomposed into two parts: coaxial part and rotational part. Based on these, the complex three dimensional (3-D) problem involving the rotation of principal stress axes is simplified to the combination of the 3-D coaxial model and the theory about pure rotation of principal stress axes that is only around one principal stress axes. The difficulty of analysis is reduced significantly. The concrete calculating method of general 3-D problem is provided and other applications are also presented.展开更多
The split Hopkinson pressure bar （SHPB） method is used to investigate the dynamic behavior of the artificial frozen soil under the nearly uniaxial strain and uniaxial stress conditions. The tests are conducted at th...The split Hopkinson pressure bar （SHPB） method is used to investigate the dynamic behavior of the artificial frozen soil under the nearly uniaxial strain and uniaxial stress conditions. The tests are conducted at the temperatures of -3 ℃, -8 ℃, -13℃, -17℃, -23℃, and -28℃ and with the strain rates from 900 s^-1 to 1500 s^-1. The nearly uniaxial stress-strain curves exhibit an elastic-plastic behavior, whereas the uniaxial stress-strain curves show a brittle behavior. The compressive strength of the frozen soil exhibits the positive strain rate and negative temperature sensitivity, and the final strain of the frozen soil shows the positive strain under the nearly uniaxial strain is greater rate sensitivity. The strength of the frozen soil than that under the uniaxial stress. After the negative confinement tests, the specimens are compressed, and the visible cracks are not observed. However, the specimens are catastrophically damaged after the uniaxial SHPB tests. A phenomenological model with the thermal sensitivity is established to describe the dynamic behavior of the confined frozen soil.展开更多
基金supported by the Science for Earthquake Resilience of China Earthquake Administration(Grant No.XH14060)the National Natural Science Foundation of China(Grant No.51478135)
文摘A one-dimensional equivalent linear method （EQL） is widely used in estimating seismic ground response. For this method, the shear modulus and damping ratio of inelastic soil are supposed to be frequency independent. However, historical earthquake records and laboratory test results indicate that nonlinear soil behavior is frequency- dependent. Several frequency-dependent equivalent linear methods （FDEQL） related to the Fourier amplitude of shear strain time history have been developed to take into account the frequency-dependent soil behavior. Furthermore, the shear strain threshold plays an important role in soil behavior. For shear strains below the elastic shear strain threshold, soil behaves essentially as a linear elastic mate- rial. To consider the effect of elastic-shear-strain-threshold- and frequency-dependent soil behavior on wave propaga- tion, the shear-strain-threshold- and frequency-dependent equivalent linear method （TFDEQL） is proposed. A series of analyses is implemented for EQL, FDEQL, and TFDEQL methods. Results show that elastic-shear-strain-threshold- and frequency-dependent soil behavior plays a great influence on the computed site response, especially for the high- frequency band. Also, the effect of elastic-strain-threshold- and frequency-dependent soil behavior on the site response is analyzed from relatively weak to strong input motion, and results show that the effect is more pronounced as input motion goes from weak to strong.
基金Supported by the Program for the Scientific Research and Technology Development in Guangxi(Guikehe 415104001-22)the Science and Technology Planning Project of Guangxi(Guikegong 1598006-5-13)+2 种基金the Experiment Station for Selenium Featured Crops in Guangxi(Gui TS2016011)the Fund for Science and Technology Development and Scientific Research of Guangxi Academy of Agricultural Sciences(Guinongke 2015JM23,2017JM01,2017JM03)the Innovation-Driven Development Special Fund Project of Guangxi(Guike AA17202019-1&Guike AA17202019-4)
文摘To provide reference for selenium resource exploitation of soil,many selenium-tolerant strains were isolated from selenium-rich soil in Guangxi. The dilution spread plate method and selenium-added culture method were used to screen the selenium-tolerant strains from the soils which were sampled from the main Selenium-rich areas such as Yongfu,Bama,Yulin Hanshan,Guiping and Tengxian. The results showed that 8 strains with high selenium tolerance were obtained,which could tolerate the selenium concentration above 10 000 μg/m L in solid medium. Among the 8 strains,YLB1-33 showed the highest selenium tolerance,and it could still grow weakly in the solid medium with selenium concentration of 29 000 μg/m L. The sequencing of 16 S rD NA and phylogenetic analysis showed that YLB1-6 was identified as Bacillus cereus,BMB2-1 and TXB1-8 were identified as Bacillus pumilus,GPB2-5 was identified as Bacillus thuringiensis,YLB1-26 and YLB1-33 were identified as Bacillus licheniformis,and YLB1-2 and YFB1-8 were identified as Serratia marcescens. The finding of selenium-tolerance strains had potential application value on promoting the utilization of selenium soil resources and the development of selenium-rich agricultural products in Guangxi.
基金supported by the National Natural Science Foundation of China (No.50578121)
文摘This paper presents an alternative analytical technique to study a plane strain consolidation of a poroelastic soil by taking into account the anisotropy of permeability. From the governing equations of a saturated poroelastic soil, the relationship of basic variables for a point of a soil layer is established between the ground surface （z=0） and the depth z in the Laplace-Fourier transform domain. Combined with the boundary conditions, an exact solution is derived for plane strain Biot＇s consolidation of a finite soil layer with anisotropic permeability in the transform domain. Numerical inversions of the Laplace transform and the Fourier transform are adopted to obtain the actual solution in the physical domain. Numerical results of plane strain Biot＇s consolidation for a single soil layer show that the anisotropic of permeability has a great influence on the consolidation behavior of the soils.
基金National Natural Science Foundation of China(Grant No.59978049)
文摘A new semi-empirical formula for evaluating the residual strain of soils under earthquake loading is presented in this paper based on the incremental method and the increment model proposed by the authors.When the incident loading is uniform,the results calculated by the new formula are nearly the same as those by the existing formula.For excitation of the random earthquake loading,the results calculated by the new formula are compared to the results obtained by dynamic triaxial tests.The dynamic triaxial tests had been performed considering different seismic waves,confining stresses, consolidation ratios,and types of cohesive soils.The comparison between the calculated and tested results indicate that the presented formula can efficiently and practically describe the time-dependent process of the soil residual strains under actual seismic loads.
基金Supported by National Natural Science Foundation of China(31070361)Beijing Outstanding Teaching Team Project about Ecology in 2008+2 种基金The Fundamental Research Funds for the Central Universities (0910KYZY43)Undergraduate Research and Training Project of Minzu University of China (URTP201011115)Quality Course Project of Minzu University of China in 2011
文摘[Objective] The aim was to screen strains producing alkaline protease from soil and study the conditions for enzyme production.[Method] Eight strains producing alkaline protease were isolated from soil through plate isolation,and the ability of enzyme production was measured by filter paper and Folin-phenol method.The strain with the strongest ability of enzyme production was screened as a candidate strain,then the factors influencing the ability of enzyme production was studied,finally the conditions for enzyme production was optimized through orthogonal test.[Result] No.5 strain was screened as a candidate strain due to its strong ability of enzyme production(6.00 U/ml),which accounted for 134.1% of that of Bacillus licheniformis,and it was gram-positive bacterium belonging to Clostridium.Orthogonal test showed that the optimal condition for producing protease was an environment with pH=11,0.3% of sucrose and 0.8% of peptone in the fermentation medium,and inoculation amount was 105 cfu/ml.In addition,peptone had significant impact on the level of enzyme production.[Conclusion] The study could provide theoretical references for the screening of strains producing alkaline protease.
文摘In the light of matrix theory, the character of stress increment which causes the rotation of principal stress axes is analysed and the general stress increment is decomposed into two parts: coaxial part and rotational part. Based on these, the complex three dimensional (3-D) problem involving the rotation of principal stress axes is simplified to the combination of the 3-D coaxial model and the theory about pure rotation of principal stress axes that is only around one principal stress axes. The difficulty of analysis is reduced significantly. The concrete calculating method of general 3-D problem is provided and other applications are also presented.
基金supported by the National Natural Science Foundation of China (No.11172251)the Open Fund of State Key Laboratory of Frozen Soil Engineering (No.SKLFSE201001)the Fundamental Research Funds for the Central Universities (No.SWJTU09CX069)
文摘The split Hopkinson pressure bar （SHPB） method is used to investigate the dynamic behavior of the artificial frozen soil under the nearly uniaxial strain and uniaxial stress conditions. The tests are conducted at the temperatures of -3 ℃, -8 ℃, -13℃, -17℃, -23℃, and -28℃ and with the strain rates from 900 s^-1 to 1500 s^-1. The nearly uniaxial stress-strain curves exhibit an elastic-plastic behavior, whereas the uniaxial stress-strain curves show a brittle behavior. The compressive strength of the frozen soil exhibits the positive strain rate and negative temperature sensitivity, and the final strain of the frozen soil shows the positive strain under the nearly uniaxial strain is greater rate sensitivity. The strength of the frozen soil than that under the uniaxial stress. After the negative confinement tests, the specimens are compressed, and the visible cracks are not observed. However, the specimens are catastrophically damaged after the uniaxial SHPB tests. A phenomenological model with the thermal sensitivity is established to describe the dynamic behavior of the confined frozen soil.
